Application of a frequency quintupled Nd:YAG source (λ=213 nm) for laser ablation inductively coupled plasma mass spectrometric analysis of minerals

Abstract

This paper reports the use a frequency quintupled Nd:YAG laser (λ=213 nm) for laser ablation of minerals for ICP-MS analysis. The fifth harmonic was produced by in-house modification to an existing frequency quadrupled Nd:YAG laser (λ=266 nm), using commercially available optical components. The maximum pulse energy of the 213 nm output is 7.5 mJ per pulse, based on an output of 350 mJ per pulse at 1064 nm. The pulse energy is controlled and attenuated by a wave plate and MgF₂ polariser combination. The laser sampling system was coupled to an enhanced sensitivity ICP-MS system. Comparison of time resolved signals for extended analyses of several materials using 213 and 266 nm for ablation demonstrates that (1) 213 nm laser ablation greatly reduces the incidence of catastrophic ablation of strongly cleaved minerals in thin section, owing to higher absorption; (2) in each case, 213 nm laser ablation produces a longer, flatter, higher intensity signal than conventional 266 nm laser ablation, suggesting a larger volume of transportable particulate is produced; and (3) inter-element fractionation is reduced during analysis using the 213 nm laser ablation system. This study is the first reported use of frequency quintupled laser ablation microprobe (LAM)–ICP-MS.